Semiconductor device

ABSTRACT

A semiconductor device includes a first type semiconductor structure, an active structure, and a contact layer. The first type semiconductor structure includes a first lattice constant, a first side and a second side opposite to the first side. The active structure is on the first side of the first type semiconductor structure and emits a radiation, and the radiation has a peak wavelength between 1000 nm and 2000 nm. The contact layer is on the second side of the first type semiconductor structure and includes a second lattice constant. A difference between the first lattice constant and the second lattice constant is at least 0.5%.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the right of priority based on TW ApplicationSerial No. 107146841, filed on Dec. 24, 2018, and the content of whichis hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The application relates to a semiconductor device, and moreparticularly, to a semiconductor device including lattice constantdifferences.

DESCRIPTION OF BACKGROUND ART

Technology is changing with each passing day, and the semiconductordevice plays a very important role in the fields of data transportation,energy conversion, and so on. The research and development of therelated materials is ongoing. For example, the semiconductor materialcan apply in various optoelectronic devices, such as light emittingdiode (LED), laser diode (LD), solar cell, power device, acoustic wavesensor, and so on. It can also be applied in the fields of illustration,display, communication, sensing, power system and so on.

The light emitting principle of the light-emitting diode is providingcurrent to combine the electron in n type semiconductor layer and thehole in the p type semiconductor layer, in order to convert theelectrical energy to optical energy. The advantages of thelight-emitting diode is low power consumption and long lifetime, and thelight-emitting diode therefore replaces the conventional light sourceand is widely used in traffic sign, back light module, variousillumination and medical instrument, and so on. The light-emitting diodewhich emits near infrared light also has huge market potential in thefields of sensing system, recognition system, surveillance system andvehicle light source.

SUMMARY OF THE APPLICATION

A semiconductor device includes a first type semiconductor structure, anactive structure, and a contact layer. The first type semiconductorstructure includes a first lattice constant, a first side and a secondside opposite to the first side. The active structure is on the firstside of the first type semiconductor structure and emits a radiation,and the radiation has a peak wavelength between 1000 nm and 2000 nm. Thecontact layer is on the second side and includes a second latticeconstant. A difference between the first lattice constant and the secondlattice constant is at least 0.5%.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments in the present disclosure will be explained according tothe drawings. It should be noted that every layer or structure is onlyfor exemplification and not drawn to scale. In fact, to clearly show thecharacters in the present disclosure, the sizes of the layers andstructures can be arbitrarily enlarged or shrunk.

FIG. 1 shows a cross-sectional view of a semiconductor device inaccordance with one embodiment of the present application.

FIG. 2 shows a cross-sectional view of the semiconductor device inaccordance with one embodiment of the present application.

FIG. 3 shows a top view of a semiconductor device in accordance with oneembodiment of the present application.

FIGS. 4A˜4B show cross-sectional views of different steps when producingthe semiconductor device in accordance with the embodiment of thepresent application shown in FIG. 2.

FIG. 5 is a graph showing the relationship between the elementconcentration and the depth of a part of the semiconductor device inaccordance with one embodiment of the present application.

FIG. 6 shows a cross-sectional view of a semiconductor device inaccordance with one embodiment of the present application.

FIG. 7 shows a cross-sectional view of a semiconductor device inaccordance with one embodiment of the present application.

FIG. 8 shows a cross-sectional view of a package structure of asemiconductor device in accordance with one embodiment of the presentapplication.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Some embodiments are described below to make the person having ordinaryskill in the art understand the present disclosure more easily. However,the embodiments are just for exemplification and not for limiting thescope of the present invention. It can be understood that the personhaving ordinary skill in the art can modify the following embodimentsaccording to his requirement, for example, changing the order ofprocesses and/or including more steps or less steps than thedescription.

Moreover, other structures or steps can be incorporated in the followingembodiments. For example, the description of “forming a secondlayer/structure on the first layer/structure” can include the embodimentthat the first layer/structure directly contacts the secondlayer/structure. It may include the embodiment that the firstlayer/structure indirectly contacts the second layer/structure, andother layer/structure exists between the first layer/structure and thesecond layer/structure. Besides, the spatial relative relationshipbetween the first layer/structure and the second layer/structure maychange according to the operation or usage of the device. On the otherhand, different embodiments in the present disclosure may have repeatednumbers and/or letters. The repetition is for simplification and clearand not for representing the relationship between different embodiments.Furthermore, in the present disclosure, the layer/structure with adescription of “a layer/structure substantially consisting of Xmaterial” may still contain a dopant or unavoidable impurities.

In the embodiments of the present disclosure, if not describedotherwise, the above-mentioned chemical formulas include “stoichiometriccompounds” and “non-stoichiometric compounds”. A “stoichiometriccompound” is, for example, a compound in which the total number of atomsof III-group elements is the same as the total number of atoms ofV-group elements. On the contrary, a “non-stoichiometric compound” is,for example, a compound in which the total number of atoms of III-groupelements is different from the total number of atoms of V-groupelements. For example, a compound has a chemical formula of AlGaAsrepresents that the compound includes Al and/or Ga as III-groupelements, and As as V-group element, wherein the total number of atomsof the III-group elements (Al and/or Ga) and the total number of atomsof the V-group elements (As) may be the same or different.

In addition, if the above-mentioned compounds represented by thechemical formulas are stoichiometric compounds, then AlGaAs representsfor Al_(x1)Ga_((1-x1))As, wherein 0<x1<1; AlInP represents forAl_(x2)In_((1-x2))P, wherein 0<x2<1; AlGaInP represents for(Al_(y1)Ga_((1-y1)))_(1-x3)In_(x3)P, wherein 0<x3<1, and 0<y1<1;AlGaInAs represents for (Al_(y2)Ga_((1-y2)))_(1-x4)In_(x4)As, wherein0<x4<1

0<y2<1 ; AlGaN represents for Al_(x5)Ga_((1-x5))N, wherein 0<x5<1;AlAsSb represents for AlAs_(x6)Sb_((1-x6)), wherein 0<x6<1; InGaPrepresents for In_(x7)Ga_(1-x7)P, wherein 0<x7<1; InGaAsP represents forIn_(x8)Ga_(1-x8)As_(1-y3)P_(y3), wherein 0<x8<1, and 0<y3<1; InGaAsNrepresents for In_(x9)Ga_(1-x9)As_(1-y4)N_(y4), wherein 0<x9<1, and0<y4<1; AlGaAsP represents for Al_(x10)Ga_(1-x10)As_(1-y5)P_(y5),wherein 0<x10<1, and 0<y5<1; InGaAs represents for In_(x11)Ga_(1-x11)As,wherein 0<x11<1.

For convenience, quaternary light emitting diode is used to be one ofthe embodiments of the semiconductor device in the present disclosurehereafter. However, the semiconductor device in the present invention isnot limited to be quaternary light emitting diode. The presentdisclosure can be applied in different types of semiconductor device,such as binary light emitting diode, ternary light emitting diode orother semiconductor devices. Besides, two electrodes of thesemiconductor device can locate on opposite sides or on the same side ofthe semiconductor device. “Quaternary”, “ternary” and “binary” mentionedabove represent the semiconductor stack of the light emitting diodeincludes a compound composed of four, three or two elementsrespectively.

Some embodiments of the semiconductor device in the present disclosureare described hereafter. The semiconductor device is particularlyapplicable to light emitting device which emits near-infrared ray (NIR).When the semiconductor device is a light-emitting diode, the material ofthe contact layer and/or the window layer close to light-emittingsurface is a non-light-absorbing material. Since an absorbing wavelengthof the non-light-absorbing material is different from a light emittingwavelength of the active structure, the non-light-absorbing materialdoes not absorb the light emitted by the active structure. Therefore,the light-emitting efficiency can be enhanced. Moreover, the producingprocesses for manufacturing the light emitting device can be reducedsince no extra process is needed to remove the contact layer. Besides,the contact layer and/or the window layer can be roughened to enhancethe brightness of the semiconductor device. In some embodiments, thematerial of the active structure includes quaternary compoundsemiconductor, such as AlInGaAs or InGaAsP, and the non-light-absorbingmaterial can include a binary compound semiconductor, such as GaAs orInP. In other embodiments, the active structure includes AlInGaAs.Preferably, the active structure is substantially consisting ofAlInGaAs. In other embodiments, the active structure includes InGaAsP.Preferably, the active structure is substantially consisting of InGaAsP.

FIG. 1 shows a cross-sectional view of a semiconductor device 100 inaccordance with one embodiment of the present disclosure. Thesemiconductor device 100 includes a base 102 and a semiconductor stack Son the base 102. The semiconductor stack S includes a first contactlayer 104, a first window layer 106, a buffer layer 108, a first typesemiconductor structure 110, an active structure 112, a second typesemiconductor structure 114, a second window layer 116, and a secondcontact layer 118.

In some embodiments, the semiconductor stack S can epitaxially grow onthe base 102 or bond to the base 102. That is, the base 102 can be agrowth substrate or a non-growth substrate. The base 102 can be used tosupport the semiconductor stack S and other layer(s) or structure(s)disposed thereon. The base 102 can be transparent, semi-transparent oropaque to the light emitted by the active structure 112. The base 102can be conductive, semiconductive, or insulative. In the embodiment, thesemiconductor device 100 is vertical type, and the base 102 thereforeincludes a conductive material, such as metal material, metal alloymaterial, metal oxide material, semiconductor material orcarbon-containing material. The metal material includes copper (Cu),aluminum (Al), chromium (Cr), tin (Sn), gold (Au), nickel (Ni), titanium(Ti), platinum (Pt), lead (Pb), zinc (Zn), cadmium (Cd), antimony (Sb)or cobalt (Co). The metal alloy includes the combination of the abovemetal elements. The semiconductor material includes IV groupsemiconductor or III-V group semiconductor, such as silicon (Si),germanium (Ge), silicon carbide (SiC), gallium nitride (GaN), galliumphosphide (GaP), gallium arsenide (GaAs), gallium arsenide phosphide(AsGaP) or indium phosphide (InP). The metal oxide material can includeindium tin oxide (ITO), indium oxide (InO), tin oxide (SnO), cadmium tinoxide (CTO), antimony tin oxide (ATO), aluminum zinc oxide (AZO), zinctin oxide (ZTO), gallium doped zinc oxide (GZO), tungsten doped indiumoxide (IWO), zinc oxide (ZnO) or indium zinc oxide (IZO). Thecarbon-containing material can include diamond-like carbon (DLC) orgraphene. In another embodiment, when the semiconductor device 100 isnon-vertical type, the substrate can include insulating material, suchas sapphire, glass, insulating nitride (ex: silicon nitride, SiN) orinsulating oxide (ex: silicon oxide, SiO₂). In the embodiment, thesemiconductor device 100 is a near infrared light-emitting device, andthe material of the base 102 includes indium phosphide (InP) or galliumarsenide (GaAs). Preferably, the material of the base 102 issubstantially consisting of InP or GaAs.

In this embodiment, the base 102 is a growth substrate and the secondcontact layer 118, the second window layer 116, the second typesemiconductor structure 114, the active structure 112, the first typesemiconductor structure 110, the buffer layer 108, the first windowlayer 106, and the first contact layer 104 can be sequentially formed onthe base 102 by expitaxial growth method. The expitaxial growth methodincludes metal organic chemical vapor deposition (MOCVD), molecular beamepitaxy (MBE), hydride vapor deposition (HYPE) and the similar method orthe combination of the above method.

In some embodiments, the material of the first contact layer 104, thefirst window layer 106, the first type semiconductor structure 110, theactive structure 112, the second type semiconductor structure 114, thesecond window layer 116, and the second contact layer 118 canrespectively include III-V group compound semiconductor material, suchas AlGaInAs

AlGaAs

AlInAs

GaInAs

AlAs

GaAs

InAs

AlGaInP

AlGaP

AlInP

GaInP

AlP

GaP

InP

AlInGaN

AlInN

AlGaN

InGaN

AlAsSb

AlSb

AsSb

InGaAsP

InAsP

GaAsP

InGaAsN

InAsN

GaAsN

InN

AlGaAsP

AlAsP or other similar III-V group compound semiconductor material.

As shown in FIG. 1, the active structure 112 locates between the firsttype semiconductor structure 110 and the second type semiconductorstructure 114. When the semiconductor device 100 is a light-emittingdevice, the first type semiconductor structure 110 and the second typesemiconductor structure 114 can be cladding layers and/or confinementlayers to provide electrons/holes and holes/electrons respectively, andtheir band gaps are higher than a band gap of the active structure 112to increase the combination probability of electrons and holes in theactive structure 112 to emit light. The active structure 112 can emit aradiation. For example, for the near infrared light-emitting device, theradiation has a peak wavelength between 1000 nm and 2000 nm, andpreferably between 1200 nm and 1800 nm, preferably between 1250 nm and1650 nm.

The semiconductor device 100 can include a single heterostructure (SH),a double heterostructure (DH), a double-side double heterostructure(DDH), or a multi-quantum well structure (MQW). In some embodiments, theactive structure 112 is multi-quantum well structure and includes aplurality of barrier layers and a plurality of well layers alternatelystacked. The barrier layer has a band gap than that of the well layer.In some embodiments, the barrier layers and the well layers canrespectively include quaternary material or ternary material. In someembodiments, the active structure 112 can include aluminum (Al), gallium(Ga), indium (In), phosphor (P) or arsenide (As), and preferably thequaternary compound devoid of nitrogen element, such as AlGaInAs orInGaAsP.

As shown in FIG. 1, the first type semiconductor structure 110 and thesecond type semiconductor structure 114 locate on opposite sides of theactive structure 112 respectively. The first type semiconductorstructure 110 and the second type semiconductor structure 114 can be asingle layer or multiple layers and include band gaps higher than theband gap of the active structure 112 for confining the carriers in theactive structure 112 and effectively prevent the carriers overflow fromthe active structure 112, and/or respectively provides electrodes andholes into the active structure 112. In some embodiments, the first typesemiconductor structure 110 and the second type semiconductor structure114 can include III-V group semiconductor materials as shown above. Insome embodiment, the first type semiconductor structure 110 and thesecond type semiconductor structure 114 preferably include aluminum(Al), gallium (Ga), indium (In), phosphor (P) or arsenide (As) or thecombination of the above elements, and preferably the ternary compoundor binary compound compound devoid of nitrogen element, such as InAlAsor InP.

In some embodiments, the first type semiconductor structure 110 has afirst conductive type and the second type semiconductor structure 114has a second conductive type different from the first conductive type.For example, the first conductive type and the second conductive typecan be p type and n type respectively, or n type and p typerespectively. The first type semiconductor structure 110 and the secondtype semiconductor structure 114 have different conductive types viaadding different dopants. For example, the first type semiconductorstructure 110 includes a dopant, and the second type semiconductorstructure 114 includes another dopant different from the dopant in thefirst type semiconductor structure 110. More specifically, the dopantsmentioned above can include magnesium (Mg), zinc (Zn), silicon (Si) ortellurium (Te). In some embodiments, the doping procedure in the firsttype semiconductor structure 110 and the second type semiconductorstructure 114 can be performed by in-situ doping during epitaxial growthprocess and/or implanting p type dopant or n type dopant after epitaxialgrowth process. For example, in the embodiment, the dopant in the firsttype semiconductor structure 110 is zinc and the dopant in the secondtype semiconductor structure 114 is silicon.

In one embodiment, a doping concentration of the dopant in the firsttype semiconductor structure 110 or a doping concentration of the dopantin the second type semiconductor structure 114 can be between 1×10¹⁶/cm³and 5×10¹⁸/cm³. In one embodiment, the doping concentration of thedopant in the first type semiconductor structure 110 can be higher thanthe doping concentration of the dopant in the second type semiconductorstructure structure 114. For example, the doping concentration of thedopant in the first type semiconductor structure 110 is between1×10¹⁷/cm³ and 1×10¹⁸/cm³, and more preferably between 3×10¹⁷/cm³ and8×10¹⁷/cm³. The doping concentration of the dopant in the second typesemiconductor structure 114 is between 3×10¹⁶/cm³ and 1×10¹⁸/cm³, andmore preferably preferably between 5×10¹⁶/cm³ and 9×10¹⁷/cm³. In someembodiments, a thickness of the first type semiconductor structure 110and a thickness of the second type semiconductor structure 114 can berespectively between 100 nm and 1200 nm, preferably between 200 nm and1000 nm.

In the embodiment of the present disclosure, the first contact layer 104and the first window layer 106 include the same non-light-absorbingmaterial. The non-light-absorbing material can be GaAs. The first typesemiconductor structure 110, the active structure 112, the second typesemiconductor structure 114, the second window layer 116, and the secondcontact layer 118 can respectively include any suitable material, andthe present disclosure is not for limit the material of thestructures/layers. In other embodiment, the first contact layer 104 andthe first window layer 106 can respectively include differentnon-light-absorbing materials, such as GaAs and InP. Moreover, thesecond contact layer 118 and the second window layer 116 can include thesame or different non-light-absorbing materials. Or in other embodiment,the first contact layer 104, the first window layer 106, the secondcontact layer 118, and the second window layer 116 includenon-light-absorbing materials, and those non-light-absorbing materialscan be the same or different.

As shown in FIG. 1, the semiconductor device 100 includes the firstcontact layer 104 on the first type semiconductor structure 110, and thefirst type semiconductor structure 110 is between the first contactlayer 104 and base 102. More specifically, the first type semiconductorstructure 110 includes a first side S1 and a second side S2 opposite tothe first side S1, and the second side S2 is farer away from the base102 than the first side S1 to the base 102. The active structure 112locates on the first sides S1 and the first contact layer 104 locates onthe second side S2. A band gap of the first contact layer 104 is higherthan a band gap of the active structure 112 and a band gap of the firsttype semiconductor structure 110 to prevent the efficiency of thesemiconductor device 100 from decreasing because the first contact layer104 absorbs light emitted from the active structure 112. In oneembodiment, the difference between the band gap of the first contactlayer 104 and the band gap of the active structure 112 is between 0.3 eVand 0.8 eV, and more preferably between 0.4 eV and 0.7 eV.

Moreover, the first type semiconductor structure 110 includes a firstlattice constant and the first contact layer 104 includes a secondlattice constant. The first lattice constant is different from thesecond lattice constant, that is, the first type semiconductor structure110 and the first contact layer 104 are lattice mismatched. When thefirst type semiconductor structure 110 is composed of a layer, a latticeconstant of the layer is defined as the first lattice constant. When thefirst type semiconductor structure 110 is composed of multiple layers,the mean value of the lattice constants of the multiple layers isdefined as the first lattice constant. In some embodiments, thedifference of the second lattice constant and the first lattice constantis at least 0.5%, preferably between 1% and 6%, and preferably between2% and 5%, and more preferably between 3% and 4.5%. The difference D1between the second lattice constant and the first lattice constant iscalculated from the equation (1) listed below, wherein dl represents thefirst lattice constant and d2 represents the the second latticeconstant.

Difference D1=((d2−d1))/d2×100%   equation (1)

In the embodiment, the material of the first type semiconductorstructure 110 includes In_(0.53)Al_(0.47)As and the first latticeconstant is 5.848. Preferably, the material of the first typesemiconductor structure 110 is substantially consisting ofIn_(0.53)Al_(0.47)As. The material of the first contact layer 104includes GaAs and the second lattice constant is 5.653. Preferably, thematerial of the first contact layer 104 is substantially consisting ofGaAs. The difference of the second lattice constant and the firstlattice constant is 3.45%. Moreover, the lattice constants can beacquired by any applicable methods. For example, the diffraction patternacquired by transmission electron microscopy (TEM) can be used toanalyze the lattice constants of the first type semiconductor structure110 and the first contact layer 104, or the lattice constants can bedetermined by X-ray diffraction (XRD). In the present application, ifnot specifically mention, the term “lattice constant” means the latticeconstant a0 of a substantially unstrained layer.

In one embodiment, a thickness of the first contact layer 104 can bebetween 5 nm and 100 nm, such as 50 nm. Besides, a surface of the firstcontact layer 104 can optionally include a roughing structure todecrease the probability of total reflection of the light emitted fromthe active structure 112 incurred in the semiconductor stack S.Therefore, the light extraction efficiency can be enhanced, and thebrightness of the semiconductor device 100 can be further increased.

As shown in FIG. 1, the first window layer 106 is between the firstcontact layer 104 and the first type semiconductor structure 110. Thefirst window layer 106 can increase the light extraction efficiency ofthe semiconductor device 100, and/or facilitate the current evenspreading in the semiconductor stack S. In one embodiment, the firstwindow window layer 106 and the first contact layer 104 include the samematerial. Therefore, the first window layer 106 and the first contactlayer 104 includes the same lattice constant (both of them are secondlattice constant), and the difference between the second latticeconstant and the first lattice constant of the first type semiconductorstructure 110 is at least 0.5%. For example, the material of the firstcontact layer 104 and the first window layer 106 both include GaAs.Preferably, the material of the first contact layer 104 and the firstwindow layer layer 106 are substantially consisting of GaAs. In otherembodiment, the first contact layer 104 and the first window layer 106include different materials, and the window layer 106 includes a latticeconstant. The difference of the lattice constant of the window layer 106and the first lattice constant is lower than 0.5%. In other embodiment,the material of the first window layer 106 can be the same as that ofthe base 102. For example, the first contact layer 104 includes GaAs andthe first window layer 104 and the base 102 both include InP.Preferably, the first contact layer 104 is substantially consisting ofGaAs and the first window layer 104 and the base 102 are substantiallyconsisting of InP.

Besides, the conductive types of the first contact layer 104 and thefirst window layer 106 can be the same as that of the first typesemiconductor structure 110. For example, the conductive types of thefirst contact layer 104, the first window layer 106, and the first typesemiconductor structure 110 are p type, and the first contact layer 104,the first window layer 106 and the first type semiconductor structure110 includes the same dopant, such as zinc. The doping procedure in thefirst contact layer 104 and the first window layer 106 can be conductedby in-situ doping during epitaxial growth process and/or implantingdopants after epitaxial growth process. The doping concentration of thedopant in the first contact layer 104 is higher than the dopingconcentration of the dopant in the first type semiconductor structure110, and the doping concentration of the dopant in the first contactlayer 104 is higher than 1×10¹⁸/cm³ to have a lower electricalresistance between the first contact layer 104 and the electrodestructure thereon. The doping concentration of the dopant in the firstcontact layer 104 is preferably between 2×10¹⁸/cm³ and 5×10¹⁹/cm³, forexample. The first window layer 106 includes a thicker thickness or/andsmaller doping concentration than that of the first type semiconductorstructure 110, in order to increase the light extraction efficiency orimprove the lateral current spreading ability.

The doping concentration of the dopant in the first contact layer 104 isdifferent from the doping concentration of the dopant in the firstwindow layer 106. In some embodiments, the doping concentration of thedopant in the first window layer 106 is lower than that in the firstcontact layer 104. In one embodiment, the doping concentration of thedopant in the first contact layer 104 is between 2×10¹⁶/cm³ and1×10¹⁹/cm³, preferably between 4×10¹⁶/cm³ and 8×10¹⁸/cm³.

In some embodiments, a thickness of the first window layer 106 can bethicker than a thickness of the first contact layer 104. In oneembodiment, the thickness of the first window layer 106 can be between300 nm and 10000 nm, and preferable between 500 nm and 8000 nm. In theembodiment, the thickness of the first window layer 106 is 7000 nm.

As shown in FIG. 1, a buffer layer 108 locates between the first windowlayer 106 and the first type semiconductor structure 110 to moderate theenergy level difference between the first type semiconductor structure110 and the first window layer 106. More specifically, a valence bandenergy (Ev) difference exists between a valence band level of the firstwindow layer 106 and a valence band level of the first typesemiconductor structure 110, and a conduction band energy (Ec)difference exists between a conduction band level of the first windowlayer 106 and a conduction band level of the first type semiconductorstructure 110. When the valence band energy difference and/or theconduction band energy difference are/is too large, an additionalvoltage is needed for the carriers to flow, which results in a higherforward voltage (Vf) and smaller saturation current of the semiconductordevice 100 or cause failure of the semiconductor device 100 ahead oftime. Therefore, the buffer layer 108 between the first window layer 106and the first type semiconductor structure 110 can avoid the problemsmentioned above. The buffer layer 108 includes a valence band levelbetween that of the first type semiconductor structure 110 and that ofthe first window layer 106. The buffer layer 108 further includes aconduction band level between that of the first type semiconductorstructure 110 and that of the first window layer 106. Therefore, theenergy level difference between the first type semiconductor structure110 and the first window layer 106 can be moderated, and the reliabilityof the semiconductor device 100 can be improved. In another embodiment,the window layer 106 can be optionally incorporated into thesemiconductor device 100. When the semiconductor device 100 does notinclude the first window layer 106, the buffer layer 108 is between thefirst contact layer 104 and the first type semiconductor structure 110,and the buffer layer 108 directly contacts the first contact layer 104and the first type semiconductor structure 110. As mentioned above, thebuffer layer 108 is able to moderate the energy level difference betweenthe first contact layer 104 and first type semiconductor structure 110.

In one embodiment, the material of the buffer layer 108 can includequaternary semiconductor compound, such as AlGaInAs or InGaAsP. When thefirst contact layer 104 includes GaAs and the first type semiconductorstructure 110 includes InAlAs, the material of the buffer layer includes(Al_(x)Ga_(1-x))_(0.47)In_(0.53)As, wherein 0<x<1. Preferably, when thefirst contact layer 104 is substantially consisting of GaAs and thefirst type semiconductor structure 110 is substantially consisting ofInAlAs, the material of the buffer layer is substantially consisting of(Al_(x)Ga_(1-x))_(0.47)In_(0.53)As, wherein 0<x<1. In anotherembodiment, when the first contact layer 104 includes GaAs and the firsttype semiconductor structure 110 includes InP, the material of thebuffer layer includes InGaAsP. Preferably, when the first contact layer104 is substantially consisting of GaAs and the first type semiconductorstructure 110 is substantially consisting of InP, the material of thebuffer layer is substantially consisting of InGaAsP.

When the buffer layer 108 locates between the first type semiconductorstructure 110 and the first window layer 106 (or the first contact layer104), the buffer layer 108, the first type semiconductor structure 110and the first window layer 106 (or the first contact layer 104) have thesame conductive type, and all of them can include the same dopant. Inone embodiment, the doping concentration of the dopant in the bufferlayer 108 can be between 5×10¹⁶/cm³ and 2×10¹⁸/cm³, preferably between5×10¹⁷/cm³ and 1×10¹⁸/cm³. Besides, the thickness of the buffer layer108 can be 10 nm and 200 nm, such as 100 nm.

In some embodiments, the semiconductor device 100 can be devoid of thebuffer layer 108 so the window layer 106 directly contact the first typesemiconductor structure 110. In addition, the position and the amount ofthe buffer layer 108 can be adjusted based on the desired character ofthe actual products. In other embodiment, the semiconductor device 100can include two or more buffer layers having the same or differentmaterial and/or doping concentration. For example, in some embodiments,an additional buffer layer (not shown) locates between the second typesemiconductor structure 114 and the second window layer 116.

As shown in FIG. 1, the second window layer 116 is between the secondtype semiconductor structure 114 and base 102, and the second windowlayer 116 is far from the second side S2 of the first type semiconductorstructure 110. In some embodiments, the material of the second windowlayer 116 can include III-V group semiconductor material. In someembodiments, the second window layer 116 can include transparentconductive material. material. For example, the material of the secondwindow layer 116 can include metal oxide material or semiconductormaterial. The metal oxide material can include indium tin oxide (ITO),indium oxide (InO), tin oxide (SnO), cadmium tin oxide (CTO), antimonytin oxide (ATO), aluminum zinc oxide (AZO), zinc tin oxide (ZTO),gallium doped zinc oxide (GZO), tungsten doped indium oxide (IWO), zincoxide (ZnO), magnesium oxide (MgO) or indium zinc oxide (IZO). Thesemiconductor material can be indium phosphide (InP), gallium arsenide(GaAs), aluminum gallium arsenide (AlGaAs) or gallium phosphide (GaP).The material of the first window layer 106 can refer to the material ofthe second window layer 116. In one embodiment, the material of thesecond window layer 116 and the material of the first window layer 106include the same, such as InP. Preferably, the material of the secondwindow layer 116 and the material of the first window layer 106 aresubstantially consisting of InP. In other embodiment, the material ofthe second window layer 116 and the material of the first window layer106 are different, and include InP and GaAs respectively. Preferably,the material of the second window layer 116 and the material of thefirst window layer 106 are substantially consisting of InP and GaAsrespectively.

The second window layer 116 has a third lattice constant different fromthe second lattice constant of the first contact layer 104. In someembodiments, the difference between the third lattice constant and thesecond lattice constant is at least 5%, such as between 1% and 6%, andpreferably 2% and 5%, and more preferably 3% and 4.5%. The third latticeconstant of the second window layer 116 can be acquired by anyapplicable methods as mentioned previously. In some embodiments, thedifference between the third lattice constant and the first latticeconstant is not greater than 0.5%. In other embodiment, the differencebetween the third lattice constant and the first lattice constant isless than 0.2% and larger than 0. The difference D2 between the thirdlattice constant and the first constant is calculated from the equation(2) listed below, wherein dl represents the first lattice constant andd3 represents the third lattice constant.

Difference D2=((d3−d1))/d3×100%   equation (2)

In one embodiment, the doping concentration of the dopant in the secondwindow layer 116 can be higher than 1×10¹⁶/cm³, such as between2×10¹⁶/cm³ and 1×10¹⁸/cm³. In some embodiments, the thickness of thesecond window layer 116 can be smaller than that of the first windowlayer 106. In other embodiment, the thickness of the second window layer116 is thicker than that of the second type semiconductor structure 114,or the doping concentration in the second window layer 116 is lower thanthat in the second type semiconductor structure 114, in order toincrease the light extraction efficiency or improve the lateral currentspreading ability. In some embodiments, the thickness of the secondwindow layer 116 can be between 100 nm and 1000 nm, such as 500 nm.

As shown in FIG. 1, the second contact layer 118 can optionally locatebetween the second window layer 116 and the base 102, and the secondcontact layer 118 is far away from the second side S2 of the first typesemiconductor structure 110. The second contact layer 118 can includeIII-V group semiconductor material as mentioned previously. Theconductive types of the second contact layer 118 and the second windowlayer 116 are the same as that of the second type semiconductorstructure 114. For example, the conductive types of the second contactlayer 118 and the second window layer 116 are the same as that of thesecond type semiconductor structure 114. For example, the conductivetypes of the second contact layer 118, the second window layer 116, andthe second type semiconductor structure 114 are all n type and includethe same dopant such as silicon. The doping concentration of the dopantin the second contact layer 118 is different from that in the secondwindow layer 116. In some embodiments, the doping concentration of thedopant in the second contact layer 118 is higher than that in the secondwindow layer 116. In one embodiment, the doping concentration of thedopant in the second contact layer 118 can be higher than 5×10¹⁷/cm³ tohave lower electrical resistance between the second contact layer 118and the base 102. The doping concentration of the dopant in the secondcontact layer 118 is between 1×10¹⁸/cm³ and 1×10²⁰/cm³, for example.

The semiconductor device 100 includes a first electrode 122 and a secondelectrode 120 on the opposite sides of the semiconductor device 100respectively. For example, in the embodiment, the first contact layer104 locates between the first type semiconductor structure 110 and thefirst electrode 122, and the base 102 locates between the secondelectrode 120 and the second type semiconductor structure 114 to form avertical type semiconductor device 100. The present disclosure is notlimited to the vertical type semiconductor device 100, in otherembodiment, the first electrode 122 and the second electrode 120 canlocate on the same side of the base 102 to form a horizontal typesemiconductor device. In one embodiment, the first contact layer 104 isbetween the first type semiconductor structure 110 and the firstelectrode 122 and only aligned to the first electrode 122.

Both of the first electrode 122 and the second electrode 120 can be usedto connect the outer power source and conduct the current into thesemiconductor device 100. In some embodiments, the materials of thefirst electrode 122 and the second electrode 120 can respectivelyinclude metal material, alloy material, metal oxide material orcarbon-containing material. For example, the metal material can includealuminum (Al), chromium (Cr), copper (Cu), tin (Sn), gold (Au), nickel(Ni), titanium (Ti), platinum (Pt), lead (Pb), zinc (Zn), cadmium (Cd),antimony (Sb) or cobalt (Co). The alloy material includes includes thecombination of the above metal elements. The metal oxide material caninclude indium tin oxide (ITO), indium oxide (InO), tin oxide (SnO),cadmium tin oxide (CTO), antimony tin oxide (ATO), aluminum zinc oxide(AZO), zinc tin oxide (ZTO), gallium doped zinc oxide (GZO), tungstendoped indium oxide (IWO), zinc oxide (ZnO) or indium zinc oxide (IZO).The carbon-containing material can include diamond-like carbon (DLC) orgraphene.

FIG. 2 shows a cross-sectional view of the semiconductor device 200 inaccordance with one embodiment of the present disclosure. FIG. 3 shows atop view of a semiconductor device 200 in accordance with one embodimentof the present disclosure. FIG. 2 is the cross-sectional view of thesemiconductor device 200 taken along line AA′ in FIG. 3. Thelayer/structure having the reference numerals in FIG. 2 identical tothose shown in FIG. 1 represents the same as those in FIG. 1. Thematerials and the characters are described above and omitted herein forbrevity. Compared to the semiconductor device 100 shown in FIG. 1, thestructures of the semiconductor stack S in the semiconductor device 200is in a reverse order because of a wafer bonding process and the firsttype semiconductor structure 110 locates between the base 102 and theactive structure 112. In this embodiment, the base 102 is a non-growthsubstrate. Furthermore, after the wafer bonding process, the secondcontact layer 118 and the second window layer 116 locate at the path oflight emitted from the active structure 112. Therefore, the secondcontact layer 118 and the second window layer 116 can also be made ofnon-light-absorbing material, and the band gaps of the second contactlayer 118 and the second window layer 116 are higher than the band gapof the active structure 112. For example, InP is used as thenon-light-absorbing material. The wafer bonding process will bedescribed below.

Compared to the semiconductor device 100 shown in FIG. 1, besides thebase 102, the semiconductor stack S, the first electrode 122 and thesecond electrode 120, the semiconductor device 200 further includes areflective structure 130, a conductive structure 140, and a bondinglayer 124 between the base 102 and semiconductor stack S. Moreover, inthe embodiment, the first contact layer 104 can be optionally omitted.The characteristics of the second contact layer 118, the second windowlayer 116, and the second type semiconductor structure 114 cancorrespond to those of the first contact layer 104, the first windowlayer 106, and the first type semiconductor structure 110, respectively.For example, the characteristics include lattice constant, dopingconcentration or thickness. In addition, the energy gap differencesamong the second contact layer 118, the second window layer 116, and thesecond type semiconductor structure 114 can also correspond to thoseamong the first contact layer 104, the first window layer 106, and thefirst type semiconductor structure 110. In the embodiment, as shown inFIGS. 2˜3, the second electrode 122 includes an electrode pad 1221approximately located on the center of a top surface of thesemiconductor stack S, and multiple extending electrodes 1222 connectedto the electrode pad 1221 and extending to the direction away from theelectrode pad 1221. The multiple extending electrodes 1222 can spreadthe current into the semiconductor stack S uniformly.

More specifically, the semiconductor device 200 includes a bonding layer124 between the reflective structure 130 and the base 102 to connect thereflective structure 130 with the base 102. In some embodiments, thebonding layer 124 includes a plurality of sub-layers (not shown), andthe material of the bonding layer 124 can include electricallyconductive material, such as metal oxide material, semiconductormaterial, metal material, metal alloy material, or carbon-containingmaterial. The metal oxide material can include indium tin oxide (ITO),indium oxide (InO), tin oxide (SnO), cadmium tin oxide (CTO), antimonytin oxide (ATO), aluminum zinc oxide (AZO), zinc tin oxide (ZTO),gallium doped zinc oxide (GZO), tungsten doped indium oxide (IWO), zincoxide (ZnO), indium cerium oxide (ICO), indium titanium oxide (ITiO),indium zinc oxide (IZO), indium gallium oxide (IGO) or gallium andaluminum co-doped zinc oxide (GAZO). The semiconductor material caninclude gallium phosphide (GaP). The metal material can include copper(Cu), aluminum (Al), tin (Sn), gold (Au), silver (Ag), nickel (Ni),titanium (Ti), platinum (Pt), lead (Pb) or tungsten (W). The metal alloyincludes the combination of the above metal elements. Thecarbon-containing material can include graphene.

The reflective structure 130 locates between the base 102 and thesemiconductor stack S to reflect the light emitted from the activestructure 112 for increasing the light extraction efficiency (LEE) ofthe semiconductor device 200. In some embodiments, the material of thereflective structure 130 can include metal material or metal alloymaterial. The metal material can include copper (Cu), aluminum (Al), tin(Sn), gold (Au), silver (Ag), platinum (Pt) or tungsten (W). The metalalloy includes the combination of the above metal elements.

In some embodiments, as shown in FIG. 2, the reflective structure 130can include a third contact layer 132, a barrier layer 134 on the thirdcontact layer 132, a reflective connecting layer 136 on the barrierlayer 134, and a reflective layer 138 on the reflective connecting layer136. The third contact layer 132 contacts the bonding layer 124 to forma low electrical contact resistance therebetween. The barrier layer 134can prevent the material of the bonding layer 124 from diffusing intothe reflective layer 138 during the manufacturing process which damagesthe reflective layer 138, therefore, the reflectance of the reflectivelayer 138 can be remained. The reflective connecting layer 136 canconnect the reflective layer 138 and the barrier layer 134. Thereflective layer 138 can reflect the light emitted from the activestructure 112. In another embodiment, the reflective structure 130 caninclude more layers. The materials of the third contact layer 132, thebarrier layer 134, the reflective connecting layer 136, and thereflective layer 138 can respectively include the same or differentmetal material or metal alloy material. The metal material can includecopper (Cu), (Cu), aluminum (Al), tin (Sn), gold (Au), silver (Ag),nickel (Ni), titanium (Ti), platinum (Pt), lead (Pb) or tungsten (W).The metal alloy material includes the combination of the above metalmaterial.

The conductive structure 140 locates between the reflective structure130 and the first contact layer 104. The conductive structure 140 istransparent to the light emitted from the active structure 112 and usedto facilitate the current conduction and spreading between the firstcontact layer 104 and the reflective structure 130. In some embodiments,the conductive structure 140 and the reflective structure 130 cancooperatively form Omni-Directional Reflector (ODR) to further improvethe light extraction efficiency (LEE) of the semiconductor device 200.In some embodiments, the material of the conductive structure 140 caninclude metal oxide material, the carbon-containing material or thecombination of the above material. The metal oxide material can includeindium tin oxide (ITO), indium oxide (InO), tin oxide (SnO), cadmium tinoxide (CTO), antimony tin oxide (ATO), aluminum zinc oxide (AZO), zinctin oxide (ZTO), gallium doped zinc oxide (GZO), tungsten doped indiumoxide (IWO), zinc oxide (ZnO), indium cerium oxide (ICO), indiumtitanium oxide (ITiO), indium zinc oxide (IZO), indium gallium oxide(IGO) or gallium and aluminum co-doped zinc oxide (GAZO). Thecarbon-containing material can include graphene.

In some embodiments, as shown in FIG. 2, the conductive structure 140includes a first conductive layer 142 on the reflective structure 130and a second conductive layer 144 between the semiconductor stack S andthe first conductive layer 142. In some embodiments, the material of thefirst conductive layer 142 is different from the material of the secondconductive layer 144. More specifically, at least one element of thematerial of the first conductive layer 142 is different from thematerial of the second conductive layer 144. For example, the materialof the first conductive layer 142 is indium zinc oxide (IZO) and thematerial of the second conductive layer 144 is indium tin oxide (ITO).

In some embodiments, as shown in FIG. 2, an insulating layer 146 locatesbetween the second conductive layer 144 and the first contact layer 104,and directly contacts the second conductive layer 144. In someembodiments, the material of the insulating layer 146 can have thetransmittance higher than 90% to the light emitted from the activestructure 112, and the material of the insulating layer 146 can includeinsulating oxide material or insulating non-oxide material. Theinsulating oxide material can include silicon oxide (SiOx) or thesimilarities. The insulating non-oxide material can include siliconnitride (SiNx), benzocyclobutene (BCB), cyclo olefin copolymer (COC) orfluorocarbon polymer. In other embodiment, the material of theinsulating layer 146 can include halide or the compound of IIA elementand VII group element, such as calcium fluoride (CaF₂) or magnesiumfluoride (MgF₂). In one embodiment, the material of the insulating layer146 has a refractive index less than 1.6.

In some embodiments, the insulating layer 146 can include a plurality ofholes passing through the insulating layer 146, so that the conductivestructure 140 directly contacts and connects electrically to thesemiconductor stack S through the plurality of holes.

In some embodiments, as shown in FIG. 2, the top surface(s) of thesecond contact layer 118 and/or the second window layer 116 can beroughened to scatter the light emitted from the active structure 112 forincreasing the light extraction efficiency of the semiconductor device200.

FIGS. 4A˜4B show cross-sectional views of different steps whenmanufacturing the semiconductor device in accordance with the embodimentof the present disclosure for describing the wafer bonding process,wherein the base 102 is a non-growth substrate. As shown in FIG. 4A, thesemiconductor stack S grows epitaxially on a growth substrate 101. Asacrificial layer 103 can be optionally located between thesemiconductor stack S and the growth substrate 101. The sacrificiallayer 103 can be removed in the following step as shown in FIG. 4B, andthe first contact layer 104, the first window layer 106, the bufferlayer 108, the first type semiconductor structure 110, the activestructure 112, the second type semiconductor structure 114, the secondwindow layer 116 and the second contact layer 118 can be separated fromthe growth substrate 101. In some embodiments, the sacrificial layer 103can be formed on the growth substrate 101 before forming the secondcontact layer 118. In some embodiments, the semiconductor device doesnot include the sacrificial layer 103, and the second contact layer 118grows directly on the growth substrate 101. In other embodiment, abuffer structure (not shown) locates between the second contact layer118 and the growth substrate 101 for decreasing the lattice defects inthe second contact layer 118 and the layers thereon so the epitaxialquality of the semiconductor stack S can be improved. In otherembodiment, the semiconductor device is devoid of the sacrificial layer103 but includes an etching stop layer (not shown) between the growthsubstrate 101 and the second contact layer 118. The etching stop layercan protect the semiconductor stack S from destroying when removing thegrowth substrate 101 by etching. The material of the etching stop layercan include InGaAs or InGaP. Preferably, the material of the etchingstop layer is substantially consisting of InGaAs or InGaP.

Moreover, in some embodiments, the sacrificial layer 103 includes amaterial having an etch selectivity different from that of the materialof the second contact layer 118. For example, the material of thesacrificial layer 103 is aluminum arsenide (AlAs). In some embodiments,the sacrificial layer 103 can be removed by wet etching process, dryetching process, laser lift-off (LLO) process or the combination of theprocesses mentioned above.

FIG. 4B shows a cross-sectional view of one of the steps whenmanufacturing the semiconductor device in accordance with the embodimentof the present disclosure. Through the wafer bonding process (or thesubstrate transfer technique), the first contact layer 104, the firstwindow layer 106, the buffer layer 108, the first type semiconductorstructure 110, the active structure 112, the second type semiconductorstructure 114, the second window layer 116 and the second contact layer118 connect to the non-growth substrate (base 102) by an bonding layer(not shown). The bonding layer locates between the first contact layer104 and the non-growth substrate. Then, the sacrificial layer 103 isremoved to separate the second contact layer 118 from the growthsubstrate 101. The order of the first contact layer 104, the firstwindow layer 106, the buffer layer 108, the first type semiconductorstructure 110, the active structure 112, the second type semiconductorstructure 114, the second window layer 116, and the second contact layer118 on the non-growth substrate is opposite to that on the growthsubstrate 101 in FIG. 4A due to the up-side-down transfer process. Morespecifically, before the up-side-down transfer process, the activestructure 112 locates between the first type semiconductor structure 110and the growth substrate 101 as shown in FIG. 4A. After the up-side-downtransfer step, the first type semiconductor structure 110 locatesbetween the non-growth substrate and the active structure 112 as shownin FIG. 4B.

Moreover, the growth substrate 101 can include semiconductor material,such as silicon carbide (SiC), gallium arsenide (GaAs), galliumphosphide (GaP), gallium arsenide phosphide (GaAsP), zinc selenide(ZnSe) or indium phosphide (InP). In some embodiments, the material ofthe growth substrate 101 can include sapphire. The materials of thenon-growth substrate and the growth substrate 101 can be the same ordifferent. In some embodiments, the non-growth substrate has differentcharacteristic from that of the growth substrate 101, for example, thenon-growth substrate has higher thermal conductivity, electricalconductivity, transparency or mechanical strength than the growthsubstrate 101.

FIG. 5 is a graph showing the relationship between the elementconcentration and the depth of a part of the semiconductor device inaccordance with one embodiment of the present disclosure. Morespecifically, FIG. 5 is a mass spectrum of a partial structure of thesemiconductor device 100 measured by secondary ion mass spectrometer(SIMS). Other technique can also be used to obtain the relationshipbetween the element concentration and the depth of a part of thesemiconductor device. The “depth” is defined as a distance measuring ina direction from the side away from the base 102 toward the side closeto the base 102, that is, the deeper the depth, the closer to thesubstrate is.

As shown in FIG. 5, according to the depths and the orders of layers inthe semiconductor device 100, the mass spectrum can be divided intoseven regions A˜G. The region A is the position correspondingapproximately to the first contact layer 104. The region B iscorresponding approximately to the first window layer 106. The region Cis corresponding approximately to the buffer layer 108. The region D iscorresponding approximately to the first type semiconductor structure110. The region E is corresponding approximately to the active structure112. The region F is corresponding approximately to the second typesemiconductor structure 114. The region G is corresponding approximatelyto the second window layer 116.

As shown in FIG. 5, the mass spectrum includes a first dopant 302, asecond dopant 304, a first element 306, a second element 308 and a thirdelement 310. The first contact layer 104, the first window layer 106,the buffer layer 108 and the first type semiconductor structure 110include the first dopant 302, which makes the conductivity types of thelayers mentioned above p-type. The first dopant is zinc (Zn). The secondtype semiconductor structure 114 and the second window layer 116 includethe second dopant 304 which makes the conductivity types of the layersmentioned above n-type. The second dopant is silicon (Si). The firstelement 306, the second element 308, and the third element 310 whichwhich can be III-group element or V-group element are the host elements(main composition) in the respective layer. In FIG. 5, the first element306 is indium, the second element 308 is aluminum, and the third element310 is gallium, which are all III-group element. The atomic mass of thefirst element 306 is larger than that of the third element 310, and theatomic mass of the second element 308 is smaller than that of the thirdelement 310. The left vertical axis indicates the concentrations of thefirst dopant 302, and the right vertical axis indicates the contents ofthe first element 306, the second element 308, and the third element310. The right right vertical axis represents the relative relationshipof the element content in each layer.

In the region A, the first dopant 302 (zinc) has the highestconcentration, which is higher than 1×10¹⁸/cm³, and the concentration ofthe first dopant 302 decreases when the depth increases. Morespecifically, the zinc dopant has a first doping concentration in theregion A and a second doping concentration in the region C. The seconddoping concentration is smaller than the first doping concentration.Moreover, the zinc dopant has a third doping concentration in the regionE. The second doping concentration is between the first dopingconcentration and the third doping concentration. The zinc dopant has afourth doping concentration in the region B, and the fourth dopingconcentration is between the first doping concentration and the seconddoping concentration. In some embodiments, a ratio of the first dopingconcentration to the second doping concentration is 10˜100.

As shown in FIG. 5, the second dopant (silicon) has the highest dopingconcentration, which is about 1×10¹⁸/cm³. More specifically, the silicondopant has a fifth doping concentration in the region G and a sixthdoping concentration in the region F. The fifth doping concentration ishigher than the sixth doping concentration. In some embodiments, a ratioof the fifth doping concentration to the sixth doping concentration isabout 2˜100.

As shown in FIG. 5, the first element 306 (indium) has the highestcontent in the region G, and the content of the first element 306increases when the depth increases. More specifically, the region C, theregion D, the region E and the region F substantially include the samecontent of indium (the first element 306), and ratios of the indiumcontent in the region C, the region D, the region E and the region F tothe indium content in the region A are all larger than 1000. Therefore,the region A can be defined as no indium, which means there is nointentional addition.

As shown in FIG. 5, the contents of the second element 308 (aluminum) inthe region D and the region F are higher than that in the region E. Theregion D and the region F substantially include the same content ofaluminum (the second element 308), and ratios of the aluminum content inthe region D and the region F to the aluminum content in region A arelarger than 1000. Therefore, the region A can be defined as no aluminum.Similarly, ratios of the aluminum content in the region D and the regionF to the aluminum content in region G are larger than 1000, and theregion G can be defined as no aluminum.

The third element 310 (gallium) has the highest content in the region Aand the region B, and the gallium content in the region E is lower thanthe gallium contents in the region A and the region B. Besides, thegallium contents in the region D, the region F and the region G are verylow compared to the gallium contents in the region A and the region B.More specifically, ratios of the gallium content in the region A to thegallium content in the region D, the region F and the region G arelarger than 1000, and therefore the region D, the region F and theregion G can be defined as no gallium.

FIG. 6 shows a cross-sectional view of a semiconductor device 300 inaccordance with one embodiment of the present disclosure. Forsimplification, the same or similar reference numerals represent thesame or similar structures. The formations and the materials of thosestructures are described above and omitted herein for brevity. In theembodiment, the semiconductor device 300 does not include the secondtype semiconductor structure 114, the second contact layer 118 and thebuffer layer 108. Moreover, the semiconductor device 300 is doubleheterostructure (DH), and the material of the active structure 112 isquaternary compound semiconductor, such as InGaAsP. The material of thefirst contact layer 104 is binary compound semiconductor, such as GaAs.In one embodiment, the materials of the first window layer 106 and thesecond window layer 116 are the same, and they are different from thematerial of the first type semiconductor structure 110. For example, thematerials of the first window layer 106 and the second window layer 116include InP. Preferably, the materials of the first window layer 106 andthe second window layer 116 are substantially consisting of InP. Inother embodiment, the materials of the first contact layer 104 and thefirst window layer 106 are the same, such as GaAs, and they aredifferent from the material of the second window layer 116 such as InP.Besides, the doping concentration of the dopant in the second windowlayer 116 of the semiconductor device 300 can be lower than 8×10¹⁷/cm³,preferably, between 1×10¹⁶/cm³ and 5×10¹⁷/cm³.

FIG. 7 shows a cross-sectional view of a semiconductor device 400 inaccordance with one embodiment of present disclosure. Forsimplification, the same or similar reference numerals represent thesame or similar structures. The formations and the materials of thosestructures are described above and omitted herein for brevity. In theembodiment, the first electrode 122 and the second electrode 120 locateon the same side of the base 102 to form a horizontal type semiconductordevice 400. In another embodiment, a connecting layer 126 is formedbetween the semiconductor stack S and the base 102, and the material ofthe connecting layer 126 can include insulating material. For example,the insulating material can include silicon oxide (SiO_(x)), aluminumoxide (Al₂O₃), aluminum nitride (AlN) or benzocyclobutene (BCB). Inthose embodiments, the base 102 can optionally have a material which istransparent to light emitted from the active structure 112, so thesemiconductor device is able to emit light from the side the base 102and the semiconductor device can be flipped and bonded to the circuitboard by the first electrode 122 and the second electrode 120.

FIG. 8 shows a cross-sectional view of a package structure of asemiconductor device in accordance with one embodiment of presentdisclosure. Referring to FIG. 8, the package structure 500 includes thesemiconductor device 100, a packaging mount 51, a carrier 53, aconnecting line 55, a contact structure 56, and an encapsulatingstructure 58. The packaging mount 51 can include ceramic material orglass material. The packaging mount 51 has a plurality of through holes52, which can be filled with electrically conductive material such asmetal for facilitating electrical conduction or/and heat dissipation.dissipation. The carrier 53 is on a surface of a side of the packagingmount 51 and also includes electrically conductive material such asmetal. The contact structure 56 is on a surface of the other side of thepackaging mount 51. In the embodiment, the contact structure 56 includescontact pads 56 a, 56 b, which can form an electrical connection withthe carrier 53 53 via the through holes 52. In one embodiment, thecontact structure 56 can further include a thermal pad (not shown)between the contact pad 56 a and the contact pad 56 b. The semiconductordevice 100 is on the carrier 53 and can be replaced by any semiconductordevice shown in the embodiments of the present disclosure mentionedabove. In the embodiment, the carrier 53 includes a first part 53 a anda second part 53 b, and the semiconductor device 100 can electricallyconnect to the second part 53 b of the carrier 53 by the connecting line55. In another embodiment, the semiconductor device 100 is disposeddirectly on the packaging mount 51 without the carrier 53 toelectrically connect to the contact structure 56.

The material of the connecting line 55 can include metal, such as gold,silver, copper, aluminum or the alloy including at least one of themetals mentioned above. The encapsulating structure 58 covers thesemiconductor device 100 to protect the semiconductor device 100. Morespecifically, the encapsulating structure 58 can include resin material,such as epoxy, or silicone. The encapsulating structure 58 can furtherincludes a plurality of wavelength conversion particles (not shown) toconvert a first light emitted by the semiconductor device 100 into asecond light. The second light has a wavelength longer than that of thefirst light. In another embodiment, the semiconductor device 100 in thepackage structure 500 can be the semiconductor device 200 or thesemiconductor device 300. In some embodiments, the package structure 500includes a plurality of the semiconductor devices 100, 200 and/or 300,and the plurality of the semiconductor devices 100, 200 and/or 300 canbe series connected, parallel connected or series-parallel connectedwith each other.

Some embodiments in the present disclosure provide a semiconductordevice including one or multiple contact layer(s) and/or window layer(s)with a material having an absorption wavelength different from that ofthe active structure to prevent the light emitted by the activestructure from absorbing by the contact layer(s) and/or the windowlayer(s). Therefore, the light-emitting efficiency of the semiconductordevice can be improved, and step(s) of removing the contact layer(s)and/or the window layer(s) for keeping the brightness of thesemiconductor device can be omitted. Besides, the contact layer(s) canbe roughened to further improve the light-emitting efficiency.

Moreover, in according to the embodiments of the present disclosure, thebuffer layer can be formed between the contact layer and thesemiconductor structures to moderate the valence band energy differenceand/or the conductive band energy difference. The buffer layer canprevent the saturated current of the semiconductor device fromdecreasing and the semiconductor device from failing ahead of time,therefore, the reliability of the semiconductor device can be improved.

The semiconductor device in the present disclosure can be applied in thefield of illumination, display, communication, sensing, and powersystem, such as lamp, surveillance, mobile phone, tablet personalcomputer, vehicle instrument panel, television, sensor, computer,wearable device (such as watch, band, or necklace), traffic signs, oroutdoor signage display.

It should be noted that the proposed various embodiments are forexplanation but not for the purpose to limit the scope of thedisclosure. Any possible modifications without departing from the spiritof the disclosure may be made and should be covered by the disclosure.The similar or same layer/structure or the layers/structures with thesame reference numeral in different embodiments have identical chemicalor physical characteristic. Besides, the elements shown in differentembodiments mentioned above could be combined or replaced by one anotherin proper situation. The connecting relationship of specificlayer/structure particularly described in one embodiment could also beapplied in another embodiment, and the subject matter which comprisesthe layers/structures in different embodiments all fall within the scopeof the following claims and their equivalents.

What is claimed is:
 1. A semiconductor device comprising a first typesemiconductor structure comprising a first lattice constant, a firstside and a second side opposite to the first side; an active structureon the first side and emitting a radiation having a peak wavelengthbetween 1000 nm and 2000 nm; and a contact layer on the second side andcomprising a second lattice constant; wherein a difference between thesecond lattice constant and the first lattice constant is at least 0.5%.2. The semiconductor device of claim 1, wherein the active structurecomprises a first element and the contact layer does not comprise thefirst element.
 3. The semiconductor device of claim 2, wherein theactive structure comprises a second element different from the firstelement, and the contact layer does not comprise the second element. 4.The semiconductor device of claim 3, wherein the first element is indiumand the second element is aluminum.
 5. The semiconductor device of claim2, wherein the first type semiconductor structure comprises the firstelement.
 6. The semiconductor device of claim 1, further comprising abuffer layer between the contact layer and the first type semiconductorstructure.
 7. The semiconductor device of claim 6, wherein the bufferlayer comprises a quaternary semiconductor compound.
 8. Thesemiconductor device of claim 6, wherein the contact layer comprises afirst dopant with a first doping concentration and the buffer layercomprises the first dopant with a second doping concentration, theactive structure comprises the first dopant with a third dopingconcentration, and the second doping concentration is between the firstdoping concentration and the third doping concentration.
 9. Thesemiconductor device of claim 2, further comprising a buffer layerbetween the contact layer and the first type semiconductor structure,wherein the buffer layer comprises the first element.
 10. Thesemiconductor device of claim 1, further comprising a window layerbetween the contact layer and the first type semiconductor structure.11. The semiconductor device of claim 10, wherein the window layer has athickness between 300 nm and 10000 nm.
 12. The semiconductor device ofclaim 10, wherein the window layer comprises the same material as ordifferent from that of the contact layer.
 13. The semiconductor deviceof claim 10, wherein the window layer has a third lattice constant and adifference between the first lattice constant and he third latticeconstant is lower than 0.5%.
 14. The semiconductor device of claim 2,further comprising a base and a second type structure between the activestructure and the base, wherein the second type structure comprises thefirst element.
 15. The semiconductor device of claim 1, wherein thecontact layer has a roughing structure.
 16. The semiconductor device ofclaim 1, wherein the contact layer has a band gap higher than that ofthe active structure.
 17. The semiconductor device of claim 1, furthercomprising a base, a first electrode and a second electrode, wherein thefirst electrode and the second electrode are located on the same side ofthe base.
 18. The semiconductor device of claim 1, further comprising abase and a bonding layer between the base and the active structure. 19.The semiconductor device of claim 1, wherein the contact layer has athird element and the active structure does not comprise the thirdelement.
 20. A package structure comprising: a packaging mount; asemiconductor device of claim 1 on the packaging mount; and anencapsulating structure covering the semiconductor device.